The larvae feed on the dead tissue (or more importantly, on the bacteria that is decomposing the dead tissue) until they've grown, then they form a pupa, that eventually hatches out into the adult form. So, if there are maggots in a casket, it is because an adult female flew in when it was open an deposited some eggs.
They migrate from the body and bury themselves in the soil where they become pupae. Predatory maggots are much more abundant at this stage, and the pioneer flies cease to be attracted to the corpse. Predatory beetles lay their eggs in the corpse and their larvae then hatch out and feed on the decaying flesh.
They scavenge corpses on the surface, but they can't dig down to a coffin. Maggots can't find a buried corpse in coffin either, unless eggs are laid on the body before it is buried.
By studying the overlap, the entomologist estimate the PMI to be about 9 days. Several insects are specialized in living in very decayed dead bodies. One example is the cheese skipper, Piophila casei, where the larvae usually occurs 3-6 months after death.
Starting on the outside of the body where they hatched, maggots use mouth hooks to scoop up the fluids oozing out of the corpse. Within a day's time, the maggots will have entered the second stage of their larval lives, as well as burrowing into the corpse.
Maggots work their magic
Larval insects gnaw small holes into the body cavities, allowing gases to escape. Tissues begin to liquefy, giving the carcass a wet appearance, followed by the release of a putrid odour.
If you are looking at a long-lasting ground casket, pick a steel or metal casket. If the grave site is low on water content or moisture, metal caskets are known to last even longer, over five decades. Under favorable weather conditions, experts say that metal caskets may even last more than that – up to 80 years.
If the coffin is sealed in a very wet, heavy clay ground, the body tends to last longer because the air is not getting to the deceased. If the ground is light, dry soil, decomposition is quicker. Generally speaking, a body takes 10 or 15 years to decompose to a skeleton.
Unless a casket is made of metal and sealed with a material that won't degrade, bugs will eventually get inside.
Some flies deposit their eggs on or near a wound or sore, the larvae that hatch burrow into the skin. Certain species' larvae will move deeper in the body and cause severe damage.
Typical symptoms of furuncular myiasis include itching, a sensation of movement, and sometimes sharp, stabbing pain. At first, people have a small red bump that may resemble a common insect bite or the beginning of a pimple (furuncle). Later, the bump enlarges, and a small opening may be visible at the center.
For the most part, however, if a non-embalmed body was viewed one year after burial, it would already be significantly decomposed, the soft tissues gone, and only the bones and some other body parts remaining.
By 50 years in, your tissues will have liquefied and disappeared, leaving behind mummified skin and tendons. Eventually these too will disintegrate, and after 80 years in that coffin, your bones will crack as the soft collagen inside them deteriorates, leaving nothing but the brittle mineral frame behind.
That seems to come down to what your casket is made of. Rats are prodigious chewers and will bite through anything they can. A wooden casket likely isn't going to keep rats out, at least not over the long term.
What's really returned to you is the person's skeleton. Once you burn off all the water, soft tissue, organs, skin, hair, cremation container/casket, etc., what you're left with is bone. When complete, the bones are allowed to cool to a temperature that they can be handled and are placed into a processing machine.
Over time, coffins underground will decompose and eventually collapse. Covering the face before closing the casket adds an extra layer of protection and dignity for the deceased's face and can act as a symbolic final goodbye.
As material in coffins, “lead helps keep out moisture and preserve the body for longer and prevent smells and toxins from a dead body escaping,” said Julie Anne Taddeo, a research professor of history at the University of Maryland.
The six feet under rule for burial may have come from a plague in London in 1665. The Lord Mayor of London ordered all the “graves shall be at least six-foot deep.” The order never said why six feet. Maybe deep enough to keep animals from digging up corpses.
"The water in the graves seriously affects the coffins already buried. Coffins are not watertight so when the grave fills with water it also fills the coffin, which decomposes and rots the bodies faster.
The process takes anywhere between three to four hours depending on the power of the retort and the mass of the body inserted.
Boiling water. It's free, it's quick, it's effective, and it kills maggots in an instant. No bug sprays or other insecticides required.
Can maggots survive being buried? “Soil, it appears, is not much of a barrier to flies.” In fact, when buried under 50 cm of soil, 35 percent of the third instar larvae survived to adulthood and dug their way out of the ground. For third instar larvae buried under 5 cm of soil, the survival rate was 43 percent.
Blow flies are attracted to dead bodies because they seek a warm, moist protein-rich source to lay their eggs. They swarm on dung for the same reason.